1. Field of the Invention
This invention relates to xerographic machines, and more particularly, to a cartridge for supplying and distributing magnetically responsive dry particulate toner material to such a machine.
2. Description of the Relevant Prior Art
In the process of xerography, a latent electrostatic image of an original is generated on a movable surface having a photoconductive material on a conductive backing which first is given a uniform electric charge over its surface, said latent image being generated by exposing the surface to the original by conventional projection techniques. Following exposure, the latent electrostatic images on the moving surface are developed at a developing station which, typically, includes one or more magnetic brushes for bringing a developer comprised of a mixture of carrier beads and toner into developing relation with the movable surface and the latent image formed thereon. The developed image is then transferred at a transfer station to a copy substrate material such as a sheet of copy paper. The toner particles, which are many times smaller than the carrier beads, adhere to and coat the surface of the carrier particles due to the electrostatic attraction therebetween. As the toner-coated carrier beads roll or tumble over the movable surface carrying the latent electrostatic image of opposite polarity to the charge on the toner, toner particles are pulled away from the carrier beads by the latent electrostatic image and deposited on the movable surface to form a developed toner image. After transfer of the image, leftover developer is removed from the movable surface, while the developed image previously transferred to the copy substrate material is fixed, as by fusing, to form a permanent copy.
As toner powder images are formed, additional toner material must be supplied to the developer mixture to replenish the toner deposited on the movable surface. Various types of toner resupply systems have been described in the prior art in, for example, U.S. Pat. Nos. 3,337,072 to Del Vecchio et al. and 4,091,765 to Lowthorp, deceased, et al. In the Del Vecchio patent, the toner container includes a hollow cylindrical sleeve having an opening in its peripheral surface through which toner material is discharged. A substantially cylindrical core having a closure portion is rotatably mounted inside the sleeve to form a closure of the sleeve opening to retain the contents therein. As the core is rotated within the sleeve, the closure portion is moved into or out of interference with the sleeve opening. Lowthorp discloses a disposable toner cartridge assembly which includes an inner tube rotatably carried in an outer tube, both of which are provided with an elongate dispensing slot extending parallel to the cartridge axis so that the slots can be placed in alignment with each other as the outer tube is rotated about the inner tube. As the slots come into alignment, toner material inside the inner sleeve is dispensed therethrough.
Another system is disclosed in U.S. Pat. No. 4,688,926 to Manno. Manno discloses a toner supply cartridge and dispensing system including a tube-like cylinder which contains a supply of fresh toner which is supported in spaced relation above a toner sump which forms part of a developer housing inside a conventional xerographic machine. Drive means are provided for rotating the cylinder. Formed in the cylinder are a plurality of differently sized toner discharge openings extending in a row along the longitudinal axis of the cylinder for the toner to pass from the cylinder into the developer housing. The plurality of toner discharge openings are sized differently from one another to regulate the quantity of toner discharged in accordance with various machine operating conditions. Control means are provided for discharging controlled amounts of fresh toner through the toner discharge openings in timed synchronization with the rotation of the cylinder. Toner is discharged when the toner discharge openings are facing the developer housing and fall by gravity into the toner sump.
Various control means for controlling the amount of toner discharged are discussed in Manno. In one embodiment, the control means includes a strip-like closure in sealing engagement with the periphery of the cylinder opposite the row of toner discharge openings. The strip has apertures formed therein corresponding to each toner discharge opening and is supported for reciprocal sliding movement on the cylinder so that the apertures in the strip periodically come into alignment with the toner discharge openings to permit the discharge of toner. Alternatively, the control means may comprise a rotatable rod which is in sealing engagement with the periphery of the cylinder opposite the row of toner discharge openings. Portions of the circumference of the rod opposite each of said toner discharge openings are removed to form a row of flats. As the rod is rotated, the flats pick up a portion of toner through the toner discharge openings and rotate to discharge the toner into the developer housing.
The systems disclosed in U.S. Pat. No. 4,688,926 are complicated from a mechanical standpoint and contain several moving parts. Hence, these toner cartridges are somewhat expensive to manufacture and careful quality control is necessary to minimize product failure. Such qualities are inherently undesirable in a product such as a toner supply cartridge which is intended to be periodically replaced when the supply of toner in the old cartridge becomes exhausted. Moreover, none of the patents discussed make any provision for the operator's ability to monitor the supply of toner remaining within the cartridge. Since the user has no way to determine how much toner remains, it is possible that the operator will be unprepared in the event of exhaustion and may not have a replacement cartridge on hand.
It would be desirable to provide a cartridge for supplying and distributing particulate toner material in a xerographic machine wherein the supply of toner material remaining within the cartridge may be easily monitored by the operator, thus ensuring timely procurement of a replacement cartridge.
It would be highly desirable to provide such a cartridge which is mechanically simple in operation, does not require close manufacturing tolerances, and is relatively inexpensive to manufacture.
It would also be desirable to provide such a cartridge which may be adapted for insertion in a wide variety of existing xerographic copying machines.